1. Field of the Invention
The present invention relates to a double rotation type double wrap scroll expander in which two drive scrolls and a driven scroll rotate synchronously, and a power generation apparatus including this scroll expander.
2. Description of the Related Art
Conventional power generation systems tend mostly to be large scale plants generating at least several hundred kW, while small scale power generation is performed mostly by simply structured engine power generators and the like. Recently, however, due to increased awareness of the need for energy conservation, passage of the Act on Special Measures Concerning Procurement of Renewable Electric Energy by Operators of Electric Utilities, and the like, a need and a market for small scale power generation are gradually increasing.
Under these circumstances, photovoltaic generation and wind force power generation are not sufficiently cost-effective, and further improvements are required to reach a level at which general use is feasible.
Japanese Patent Application Publication No. 2009-209706, meanwhile, discloses a binary power generation system exhibiting relatively favorable cost-effectiveness. This binary power generation system includes a scroll expander and a power generator, and is configured such that a working medium having a low boiling point is pressurized to high pressure using hot water or steam at 85 to 150° C. as a heat source, whereupon the working medium is expanded by the scroll expander in order to drive the small scale power generator.
Here, a scroll expander exhibits little torque variation and is therefore suitable for use in a small scale power generation system. In a scroll expander having a fixed scroll and a drive scroll, however, the drive scroll slidingly contacts with the stationary fixed scroll, and therefore a dynamic seal is required, making it difficult to secure a favorable sealing property. Further, a thrust load is exerted on the drive scroll, and therefore a bearing that supports the drive scroll rotatably is easily damaged.
A scroll fluid apparatus disclosed in Japanese Patent Application Publication No. H6-341381, on the other hand, is a double rotation type double wrap scroll fluid machine. With this type of scroll fluid machine, a favorable sealing property is obtained and the thrust load is reduced, leading to improved reliability.
More specifically, a double rotation type scroll fluid machine includes a drive scroll and a driven scroll, wherein the drive scroll and the driven scroll rotate synchronously. Hence, a dynamic seal is not required, and therefore a favorable sealing property can be secured. Further, when a double wrap scroll fluid machine is used as an expander, expansion chambers exist on both sides of the driven scroll, and therefore a thrust load exerted on the drive scroll and the driven scroll is reduced by being canceled out.